Mandated by USEPA and other government agencies throughout the world, OBD II (EOBD in Europe) was primarily developed for monitoring the vehicle's emission control systems by the Engine Control Module (ECM), which will typically display a general warning to the operator (the check engine light, or Malfunction Indicator Light-MIL) when a fault is detected. It also provides a means by which a mechanic or vehicle inspector can access engine parameters, readiness status and specific fault codes related to engine hardware that can affect emissions and engine performance. The OBD II system is accessible via a standardized communications link and cable, and a microprocessor device that implements various standardized communications protocol. Such device is known as a scan tool. Data from on-board sensors can be accessed by the scan tool at a rate of up to 50 Hz.
The United States Environmental Protection Agency (EPA) is currently taking a very clear stand in favor of OBD II (On-board Diagnostic) testing for vehicle emissions inspections, requiring all non-attainment areas to introduce OBD II testing for all vehicles (gasoline and diesel powered), model year 1996 and newer in lieu of tailpipe testing. OBD II interfaces for all vehicles model year 1996 and newer are standardized to allow for communication with an external microprocessor-based system. Canada has adopted OBD II standardization for all vehicles 1998 and newer. A very similar international system, called EOBD, is required for model year 1998 and newer vehicles in Europe. Similar systems are currently being placed in vehicles in Asian markets as well.
Current new and existing vehicle emission inspection programs typically all follow the following procedure:
The motorist drives to an inspection station when the vehicle's emission inspection is due.
The vehicle enters a dedicated inspection station.
The inspection station may charge a per test fee to the motorist.
The inspector identifies the vehicle (bar code, manually, etc.).
The inspector connects the OBD II scan tool to the vehicle's Data Link Connector (DLC) and performs the OBD download according to EPA and program regulations.
The inspector disconnects the scan tool from the vehicle.
The inspection results are logged, a VIR may be issued and the data may automatically be transmitted to a centralized database typically through a modem.
Current vehicle emission inspections are time consuming for the motorist, and expensive (rates vary between $15.00 to $25.00 and more per test). Therefore, inspections are only performed annually or biennially in order to reduce the burden for the motorist to a minimum. Vehicle performance and compliance between two inspections is not known and cannot be tracked.